Research On Torsional Vibration Characteristics Of Diesel Generator Set Shaft System In Island Mode

Diesel generator sets are widely used in ships,ports,oil fields and islands as the main energy source of the island power station system.With the increasing demand for power,a single diesel generator set can no longer meet the actual demand for electricity,multiple diesel generator sets have become the mainstream trend,and multiple diesel generator sets on the grid process is also easy to cause a large impact on the transmission system and longer oscillations.These shocks and oscillations are likely to cause fatigue damage or even breakage of the crankshaft and camshaft,oscillation damage to the diesel engine auxiliary pump and other equipment,as well as broken gears and other failures,which seriously threaten the safety of the shaft system.Therefore,this paper takes the diesel generator set of a port isolated island power station as the research object,analyses the shaft system torsional vibration transient characteristics of the diesel generator set drive system from the perspective of multi-system coupling,evaluates the shaft system operation safety,and develops the parameter intelligent optimization research of the multi-dimensional coupled system of diesel generator set in isolated island mode,so as to provide reference for the multi-system parameter adjustment,low vibration design of the drive system and the stable operation of the diesel generator set in isolated island mode.The torsional vibration equivalent model of the diesel generator set shaft system was established,based on which the torsional vibration inherent characteristics and steady-state forcing characteristics of the shaft system were analyzed,and it was found that the vibration nodes are mostly located at the crankshaft and coupling,the additional torque value of the shaft system under rated full load conditions is at a low level,the maximum additional stress of the crankshaft is 63.92 MPa,which is less than the permissible stress value of 95 MPa for the crankshaft,and the diesel generator set shaft system is within the safe range under rated conditions.Based on the idea of multi-system coupling,a multi-dimensional coupling analysis model(machine-electricity-grid coupling torsional vibration analysis model)comprising diesel generator speed control system-generator excitation system-grid load system-drive unit shaft torsional vibration system is built,and the transient variation characteristics of the shaft torsional vibration of a single diesel generator set under islanding mode are analyzed and obtained.Further,considering the problem of multiple machines on the grid,a simulation model of multiple diesel generator sets on the island system is formed and the influence of grid connection and short-circuit faults on the shaft torsional vibration characteristics of each diesel generator set under different conditions is obtained.In order to carry out a low vibration optimization analysis of the isolated system diesel generator set,the control system time domain response index and the drive system shaft system torsional vibration index were considered comprehensively,and three optimization modes were set: control system parameter optimization,mechanical system parameter optimization and overall system parameter optimization(considering both control system and mechanical system),and the improved GA-PSO optimization algorithm was used to optimize the design of the coupling system parameters,the control system parameter optimization was found to be the most effective for transient speed optimization under the same optimization-seeking objective function,and the results of the mechanical system parameter optimization were found to be more variable for different operating conditions.